The present invention relates to a method for feeding preheaters having heating elements for the feed material of glass melting installations, the feed material being applied to the uppermost heating elements with a uniform distribution, in a manner controlled by sensors.
Reports concerning the preparation of feed material for glass melting installations have been published for decades, in many cases addressing the tendency of mixtures having different components to become glued together. The mixtures are provided for glass melting for very different purposes. The causes of the tendency of the components to become glued together are manifold, and are due to their very different melting points, viscosities, particle sizes and shapes, and to thermal and mechanical influences on the transport path before the melting. Particularly disturbing here is free or bound water carried along in the feed material, as well as water vapor introduced with the exhaust gases from the downstream melt pan for heating and heat recuperation. The condensation of evaporated water contributes enormously to the tendency towards gluing together. A further disturbing effect is a tower of feed material that builds up, in an uncontrolled and non-uniform manner, above the uppermost heating lines, and in which water vapor in turn condenses.
From U.S. Pat. No. 7,494,948 B2, it is known either to store free-flowing feed quantities of glass components for glass melting ovens in the moist state at temperatures below 35° C. or to preheat them to temperatures of 100° C. or higher before supplying them to a glass melting oven. The moist feed material should contain a free water portion of from 2% to 10% and a portion of from 0.0001% to 5% of a surface-active material, preferably a water-soluble soap such as a carboxylate having 4 to 22 bound C atoms, The moist feed material can be stored and preheated to at least 150° C., and remains free-flowing without depositing. The author states that before this invention it was not possible to feed a preheater with moist feed material because at temperatures of 100° C. and higher a baking of the compound was unavoidable. The document says nothing about the particle size, but, referring to EP 11 23 903 A2, states that without a device described there having an electrostatic dust separator, fine dust particles caused environmental pollution.
From DE 10 2008 030 161 B3, a shaft-type heat exchanger is known for preheating particulate glass mixture for glass melting ovens, through which smoke gases from the oven heating are conducted in alternating and meandering horizontal smoke gas channels. The heat exchanger has numerous vertical melt material channels that are rectangular in cross-section and that intersect, staggered transversely, with the smoke gas channels and are connected to one another by openings in the channel walls in a manner intended to suction water vapor from the vertical melt material channels in the transverse direction and to prevent the entry of smoke gases into the melt material channels. However, it cannot be excluded that, due to the distances between the stated openings in the shaft walls and due to the long horizontal flow paths in the melt material, moisture will remain therein, causing gluing together of the particles of the melt material and blockage of the supply.
None of the named documents addresses the problem of distributing the feed material uniformly and in as thin a layer as possible on or over the uppermost heating gas channels, and maintaining this state.